HYPOXIA REGULATION OF VEGF/VEGF RECEPTORS IN KELOIDS

我们推测，血管内稳态的失衡可能导致瘢痕疙瘩病变的炎性边缘处的多血管状态（增生性）或稳定部分处的少血管状态（经典瘢痕疙瘩），如临床和组织学上观察到的。 稳定部分的低血供或低氧状态是诱导和延长高血供和高渗透特征的关键因素。这些特征是肉芽组织表型的特征，负责维持细胞因子和生长因子的富集环境，以持续支持真皮生长。 我们的研究将集中在血管内皮生长因子（VEGF）作为瘢痕疙瘩血管稳态的主要调节因子。 所提出的瘢痕疙瘩研究模型将建立在三个临床上不同的病变部位-炎性（增生性）、稳定性（经典瘢痕疙瘩）和中央部分（消退性瘢痕）-其代表瘢痕疙瘩形成的病理过程。 转录因子、缺氧诱导因子HIF-1和缺氧反应元件HRE在瘢痕疙瘩稳定部分缺氧诱导的VEGF表达的调节中的作用将与在炎症边缘观察到的肉芽组织表型相关地确定。血管生成刺激物VEGF、HIF-1和细胞外蛋白酶尿激酶纤溶酶原激活物uPA及其抑制剂派-1之间的相互作用将在我们独特的三个不同位点的方法中进行研究，以阐明瘢痕疙瘩中差异血管形成的分子基础。我们假设，伤口血管生成的失调有助于血管网络的差异性分布，在病变的稳定部分的血管过少或缺氧，而在炎症边缘的血管过多和通透性过高，建立瘢痕疙瘩表型的良性生长。1）证实VEGF/VEGF受体和uPA/派-1在瘢痕疙瘩的三个不同部位的人微血管内皮中与邻近的临床正常皮肤相比差异表达; 2）研究低氧应激对uPA/派-1和VEGF/VEGF受体表达、受体亲和力、研究VEGF对uPA /派-1表达的影响及其在瘢痕疙瘩血管稳态中的作用; 4）阐明转录因子HIF-1和HRE在缺氧诱导的VEGF表达中的作用。

We postulate that an imbalance in vascular homeostasis could contribute to a hypervascular state at the inflammatory border (erythematous) or a hypovascular state at the stable portion (classical keloid) of the keloid lesion, as observed clinically and histologically. The hypovascular or hypoxic state present at the stable portion is the key factor for induction and prolongation of the hypervascular and hyperpermeable features. These features, characteristic of the granulation tissue phenotype, are responsible for the maintenance of an enriched milieu of cytokines and growth factors for continuing support of dermal growth. Our study will focus on vascular endothelial growth factor (VEGF) as a major regulator of keloid vascular homeostasis. The proposed keloid study model will be established on three clinically distinct lesional sites--inflammatory (erythematous), stable (classical keloid) and central portion (regressing scar)--which represent the pathologic course of keloid formation. The role of transcription factor, hypoxia- inducible factor, HIF-1, and hypoxia-responsive element, HRE, in the regulation of hypoxic-induced VEGF expression at the stable portion of the keloid will be determined in correlation with the granulation tissue phenotype observed at the inflammatory border. The interaction between angiogenic stimuli, VEGF, HIF-1, and the extracellular proteases, urokinase plasminogen activator, uPA, and its inhibitor, PAI-1, will be investigated in our unique three-distinct-sites approach to elucidate the molecular basis of differential vascular formation in keloids. We hypothesize that a dysregulation in wound angiogenesis contributes to a differential distribution of vascular network, hypovascular or hypoxic at the stable portion of the lesion versus hypervascular and hyperpermeable at the inflammatory border, establishing the benign growth of the keloid phenotype. Our hypothesis will be tested using the following specific aims: 1) To confirm that VEGF/VEGF receptor(s) and uPA/PAI-1 are differentially expressed in human microvascular endothelium of keloids at the three distinct sites compared to adjacent clinically normal skin; 2) To study the effect of hypoxic stress on the expression of uPA/PAI-1 and VEGF/VEGF receptor(s), receptor affinity, biological functions including phosphorylation and in vitro angiogenic activity; 3) To study the effect of VEGF on the expression of uPA /PAI-1 and their role in keloid vascular homeostasis; and 4) To delineate the role of transcription factor, HIF-1, and HRE on hypoxia-induced VEGF expression.